As a rule, products wrapped in stick packs for general retail are of typically flat parallelepiped shape and ordered into a wrappable group one beside the next, with the larger faces disposed transversely to the predominating axis of the assembled group. Accordingly, the group of products will present at least one relatively small transverse dimension, and the stick pack is fashioned using simple heat seal jaws by which the projecting edges of a tubular wrapper formed around the group can be gripped and secured tight against the ends of the group without generating random creases or other imperfections that might in time allow air into the finished pack.
The above considerations do not apply to another type of stick pack on general sale, in which the products are again ordered one beside the next with the larger faces in mutual contact, though in this instance forming a much more compact group generally of square or rectangular section. The ends of this type of stick are ordinarily not sealed, but simply folded. In the event of a sealed end being required for this second type of stick pack, the seal is obtained starting from a tubular wrapper of which the trimmable ends project an appreciable distance beyond the end faces of the group of products. By virtue of this extra length, the opposite edges presented by each end of the wrapper can be pinched together. Sticks presenting this type of seal are however not readily acceptable in terms of appearance, difficult to stack, unable to retain the wrapped products in close contact one with another, and inclined to break or tear open easily at the ends.
The prior art also embraces a method for forming packets of the type described above, disclosed in patent DE 3420023 by the same applicant, which envisages the step of fashioning a tubular wrapper initially around the group of stacked products and then closing the ends of the wrapper. The process of closing each end includes a first step in which the ends are drawn flat, by inserting flat spreader means, and united by the action of sealing and crimping means designed to impress crease lines on each of the flattened ends so as to facilitate a subsequent folding step. In practice, the final step occurs with the sealed and crimped end already presenting a central portion, and two lateral portions delimited on either side of the central portion by the crease lines. The central portion is folded against the end face of the group of products and the lateral portions are then folded over the central portion.
The method described above likewise presents certain drawbacks connected principally with the step in which the sealing and crimping operations occur. In effect, a dependable closure of the ends cannot be assured when the sealing and crimping steps are combined, since the sealing jaws are not able to unite the edges of the wrapper faultlessly along the crease lines.
The object of the present invention is to set forth a method and a device free of the drawbacks mentioned above, by means of which products stacked on edge and in contact one with the next by way of their larger faces can be packaged in a sealed wrapping.